FOXBORO, Mass. — David Harris has seen pretty much everything over his 11-year NFL career. But Monday still was a first for the 33-year-old linebacker.

Harris participated in the first joint practice of his NFL career when the New England Patriots shared their Gillette Stadium practice field with the Jacksonville Jaguars for a two-and-a-half-hour session.

The Patriots are one of a handful of NFL teams to hold joint practices nearly every summer. The New York Jets, Harris’ employer for the previous 10 seasons, are not. So, lining up against new faces after just over a week of training camp was quite the new experience for Harris.

“It is a little different, because you finally get the chance to feel another opponent,” Harris told reporters after Monday’s practice. “Competition is going at a high level on both sides, and it’s a good day. It’s a good measuring stick.”

These sessions are important for Harris, too. He’s one of four Patriots linebackers wearing a “green dot” on the back of his helmet at practices, which means he has a coach-to-player communication system installed in his helmet and is in charge of relaying the coaches’ defensive calls to his teammates.

Dont’a Hightower shouldered that duty for New England in games last season, but with the Pro Bowler on the physically unable to perform list, Harris is happy to take on a responsibility he had with the Jets.

“I’m used to it,” Harris said. “I’ve been doing it my whole career. It’s no different now.”

“… There’s no Dont’a out here, but he’s been in my ear. His locker is right next to mine, so he’s always giving me tips and hints on how to place everything inside the defense. He’s been a huge help.”

Harris is on a new team in a unique practice environment, but after a decade in the league, he certainly knows what he’s doing. And he doesn’t mind taking on a leadership role for the younger players on the Patriots’ defense.

“Being in my 11th year, I do have a lot of experience, Harris said. “If a young guy wants to ask me a question about certain things, I have no problem giving them my advice. … Luckily we have a lot of leaders already, so I’m just another resource for them.”